Some middle managers will overestimate how much time and people they need for a project just so they can be on time and under budget. And once you hire someone it's really hard to get rid of them until there is a layoff cycle. And usually on layoff time there's plenty of people who are actually actively making things harder for people that need firing (they try to do work but are bad at it, which causes more work for the people that are actually productive) that you don't really get around to fire the people that are just useless.